Nonvolatile switchable Josephson junctions

In a simple bilayer geometry, a thin, microstructured ferromagnetic film spans a superconducting strip. Locally strong magnetic fringe fields at the edge of the ferromagnet quench the superconductivity, creating a weak link. The strength of the weak link can be varied between on and off by controlling the orientation of the in-plane magnetization of the ferromagnet. The observation of Shapiro steps demonstrates the ac Josephson effect in the "quenched'' state. In this switchable Josephson junction, energy is required only to change states, which are thereafter maintained in thermodynamic equilibrium. (C) 1999 American Institute of Physics. [S0021-8979(99)08703-4].